Minimum Liquid Rate for Absorption Column Calculator

Minimum Liquid Flowrate Formula:

\[ Ls_{min} = Gs \times \frac{(Y_{N+1} - Y_1)}{(\frac{Y_{N+1}}{\alpha} - X_0)} \]

Gas Flowrate on Solute Free Basis (Gs):

mol/s

Solute Free Mole Fraction of Gas in Inlet (Y_N+1):

Solute Free Mole Fraction of Gas in Outlet (Y₁):

Equilibrium Constant (α):

Solute Free Mole Fraction of Liquid in Inlet (X₀):

Minimum Liquid Flowrate (Ls_min):

mol/s

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1. What is Minimum Liquid Rate for Absorption Column?

Definition: This calculator determines the minimum liquid flowrate required in an absorption column to achieve a specified gas purification.

Purpose: It helps chemical engineers design absorption columns for gas purification processes by calculating the minimum solvent requirement.

2. How Does the Calculator Work?

The calculator uses the formula:

\[ Ls_{min} = Gs \times \frac{(Y_{N+1} - Y_1)}{(\frac{Y_{N+1}}{\alpha} - X_0)} \]

Where:

\( Ls_{min} \) — Minimum liquid flowrate (mol/s)
\( Gs \) — Gas flowrate on solute free basis (mol/s)
\( Y_{N+1} \) — Solute mole fraction in inlet gas
\( Y_1 \) — Solute mole fraction in outlet gas
\( \alpha \) — Equilibrium constant for mass transfer
\( X_0 \) — Solute mole fraction in inlet liquid

Explanation: The formula calculates the minimum solvent flow needed to achieve the desired gas purification based on equilibrium relationships.

3. Importance of Minimum Liquid Rate Calculation

Details: Proper calculation ensures efficient column operation, optimal solvent usage, and meets purification requirements without excessive costs.

4. Using the Calculator

Tips: Enter the gas flowrate, inlet and outlet gas mole fractions, equilibrium constant, and inlet liquid mole fraction. All values must be valid (denominator cannot be zero).

5. Frequently Asked Questions (FAQ)

Q1: What happens if the denominator becomes zero?
A: The calculation becomes invalid. This occurs when \( \frac{Y_{N+1}}{\alpha} = X_0 \), meaning the inlet liquid is already in equilibrium with the inlet gas.

Q2: What's a typical equilibrium constant value?
A: This varies widely (0.1-10+) depending on the gas-solvent system and temperature. For CO2 in water at 20°C, it's about 1.4-1.6.

Q3: Why use solute-free mole fractions?
A: Solute-free basis simplifies calculations as the carrier gas and solvent flows remain constant throughout the column.

Q4: How does this relate to actual operating flowrates?
A: Actual flowrates are typically 1.2-2.0 times the minimum to ensure efficient mass transfer.

Q5: What if my outlet gas mole fraction is higher than inlet?
A: This would indicate a stripping operation rather than absorption, requiring a different calculation.